My battery range: is it normal?

[CycleEye]

Hi there,

I'm pretty new to e-bikes and batteries. I've recently built a steel frame road bike commuter conversion (rear hub). It's working nicely, but my battery seemed to run down alarmingly quickly today and I'm trying to work out if it's normal or not.

These are the specs:

• A 48V 15Ah / 720Wh 30A battery: https://caprouge.com.au/collections/ebi ... pwhbk48-15
• 48V 1000W rear hub motor direct drive, no regen
• Controller, 48v, maximum current rate: 30±1A

I had run a rough estimation on the Bosch calculator tool (obviously not entirely accurate as I don't have a Bosch bike) and it returned 140km. That seems way too high though. I also used the 'divide your Wh by 12 to get km range' method, which returns 60km, and seems much more realistic.

My usage this time was: full charge yesterday, then two rides combining to 25km last night and today which pretty much ran the battery close to empty. It was pretty windy, I live in an area with decent hills, and I tend to ride with PAS level 5 and lots of throttle. So I realise those all decrease range.

The battery is more or less brand new from a reputable seller:

Tiger Shark Battery, known for its durability and water resistance. Backed with high quality BAK 18650 cells.

Built with a 30A continuous discharge, this battery is built for higher powered motors, run at maximum power

All cells used in our batteries are 100% new and tested to International Electrotechnical Commission (IEC) standard 62133-2-2017 or 2012, beware as many Australian suppliers do not mention the brand of cell used

Here's a picture of the bike for reference: https://photos.app.goo.gl/jMiYxgWuc5VfEfYr7

My question is, do you think it's reasonable that they would halve the range, if 60km is a reasonable estimate? 30km isn't ideal for my purposes.

Everything you read says you should be getting more than that, not discounting all the many variables, with 750Wh.

Thank you!

 

[Benjahmin]

You have, unfortunatley, picked a direct drive motor. They are good for high speed on the flat. They are notorious for developing low hill climbing torque and heat at lower speeds. Also stop/start riding (traffic lights etc.) will munch the battery.
A 250w rated geared hub would suite your purposes far better as they are, overall, more efficient.
You say your battery is rated 30A max, as is your controller. You also say that you ride in max assist + lots of throttle. There is no headroom in the max battery current capacity so you are working the battery very hard, close to,or on, it's limit. Think: would you run an internal combustion engine at red line revs most of the time? What result would you expect?
I think you're lucky to be getting the range you are but I suspect you won't be getting it for long stressing the battery as you are.

A '250W' motor run on a 17A controller will give you a nominal 816W at 48v. A fit road racer will develop around 600w at high power short bursts. How much power do you want?
From your description of you usage style, would a motorbike be more applicable?

 

[Nealh]

Sounds about right for 30a continuous.
To get the max range even using the dodgy Bosh calcs, one needs to use lowest power setting and no hills or wind.

 

[harrys]

You're probably burning 30 wh/mile running a 1000W motor at 20-25 mph. Your calculated rate is 720 wh/15 or 50 wh/mile.

You have to derate that 720 wh. It based on a low current draw and using all of the battery. The latter can't happen because I believe the controller shuts off your battery at 40V, where about 20% of the capacity remains. So you're looking at 570 WH. With high speed riding and using 10-20A, that number drops further. If we use 30 WH/mile, maybe an effective 450 WH.

Just the thinking of an old retired engineer here. Don't forget cold weather. Another 15-20% loss.

 

[CycleEye]

Thanks very much, yes that all makes sense!